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Science of Insulating Ducts Part 2: Specification Pitfalls

Thursday, March 23, 2017 9:43 am MDT

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JM Editors

In typical HVAC system construction, engineers and contractors will work together to produce quality systems, but sometimes, the messages between the two can become muddled in translation. This generally comes down to issues with the specifications and how they are interpreted. The results can impact the short-term and long-term cost, efficiency, accuracy, and productivity. To learn more about some of the more common specification pitfalls, we recently sat down for an interview with Steve Dockery, Vice President of Spiral Pipe of Texas. Steve will be joining us as the co-host of our live webinar, The Science of Insulating Ducts, on March 28th. We sought his input to discuss some of the common struggles he has seen contractors and sheet metal duct fabricators face when it comes to interpreting the specifications that come their way.

Steve has 41 years of experience in the duct fabrication business, and has seen a lot when it comes to specifications and fabrication. He has a unique perspective to offer as he has seen the industry and the specifications evolve over the course of his career. Below, we’ve outlined the top five avoidable specification mistakes that Steve indicated he comes across most frequently as a fabricator.

  1. Discrepancies between the specification and the notes: Specifications are the recipe that contractors use to build HVAC systems and the notes are the details and finishing touches that the system needs to be built to spec. When these two don’t line up, the contractor has to make an on-the-spot decision as to whether the specs or the notes take priority. If the notes lack the specificity needed to determine which one they should follow, then the contractors must either query the designers or make an on-the-spot decision as to which course to follow. Naturally, the second option, while more efficient, increases the likelihood that mistakes or error will occur.

    Whether to prioritize the specifications or the notes is an age-old question for contractors that has no universal yes or no answer. Engineers and system designers can help prevent confusion by clarifying which details should have the final say when fabricating and installing the ducts and ensuring that their notes are consistent with the specification.
     
  2. Outdated specs: As a ductwork fabricator, Steve explained that he sees outdated specifications on a daily basis. When the specifications have not been revisited for some time, they may call for the wrong materials or reference outdated codes and standards. These standards may require fabricators to use heavier gauges or old construction methods, which has the potential to make the system more expensive than what current standards actually require. This may also lead to discrepancies between what the specifications call for and what make sense with the rest of the design.
     
  3. Lack of specificity: Steve has found that occasionally specifications lack clarity because they are too general in description and not site-specific. Sometimes this can cause specifications to be misunderstood or misinterpreted. While misunderstood specs require time for the designer and the contractor to meet to clarify what is necessary, misinterpreted specs can actually cause the system to be built incorrectly. This increases the potential that the system may not meet code or address a site-specific concern. As such, when there is the potential for confusion in the specification, designers can save time by ensuring that their specifications are made clear in notes and that the notes line-up cohesively with the specification.
     
  4. Incorrect specs: Sometimes the specifications are simply incorrect. This can stem from a lack of familiarity as to what products and materials are best for the application or simply from relying on previous versions of an outdated specification. As such, when using preexisting specifications, designers should double-check the information to ensure that it is current and correct for the application. Additionally, to avoid writing specifications with outdated, misinformation, it is critical to design to the most current codes and standards.
     
  5. Specs that don’t account for physical space: Steve has found that evolving energy codes have created a unique dynamic between what engineers put on paper and what contractors confront at the project site. For example, when the insulation thickness must be increased to meet a specific code or standard, specifically on spiral pipes, the space required for the system naturally increases because the duct size increases. This can cause two things to happen. First, the design around the duct must be adapted to accommodate the space required for a larger duct. Second, when the duct size exceeds 25” in diameter, the duct availability for odd sizes (27”, 29”, etc.) becomes an issue as most fabrication shops don’t make odd-sized ducts larger than 25” in diameter.

There are a number of other details that go into creating high-quality, efficient duct systems, and Steve will join Johns Manville’s Brennan Hall to address these issues and more in our upcoming webinar, The Science of Insulating Ducts. Join us on March 28th at 2:00 PM ET/11:00 AM PT for this live webinar followed by an open Q&A session.

Click here to register now

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